Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes such as surface-emitting lasers (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III nitride materials. Typically, III nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, Si, formed over the substrate, one or more light emitting layers in an active region formed over the n-type layer or layers, and one or more p-type layers doped with, for example, Mg, formed over the active region. Electrical contacts are formed on the n- and p-type regions.
FIG. 1 illustrates a device described in more detail in U.S. Pat. No. 7,461,948, which is incorporated herein by reference. The device includes a plurality of light emitting diode (LED) dies 102, 104, and 106, each with a different type of secondary optic. Thus, a first type of lens 103 is mounted to the LED die 102, a second type of lens 105 is mounted to the LED die 104, and a third type of lens 107 is mounted to LED 106. The lenses 103, 105, and 107 are configured to produce different light distribution patterns from their respective LEDs 102, 104, and 106. The LEDs 102, 104, and 106 are mounted near each other on a submount 101, but are separated by a distance that is adequate to distinguish the optical centers of each LED die. While three LEDs 102, 104, and 106 are shown in FIG. 1, it should be understood that fewer, e.g., two, or additional LEDs, e.g., four or more, may be used. If desired, a plurality of submounts may be used.
The different light distribution patterns produced by the different types of secondary optics combine to produce an efficient light source having a desired illumination pattern. For example, the first LED may include a lens that produces a light distribution pattern with a maximum intensity at the center while the second LED may use a lens that produces a light distribution pattern with a maximum intensity that surrounds the maximum intensity of the pattern produced by the first LED.